The present invention relates to an organic electroluminescent element. More particularly, the present invention is concerned with an organic electroluminescent element (hereinafter sometimes abbreviated to xe2x80x9corganic EL elementxe2x80x9d) which, when used for a display and the like, is highly precise and minute, uniformly emits light, and can withstand external pressure.
Organic electroluminescent elements have heretofore been developed for use as a display. The organic electroluminescent element to be used as a display is required to have high precision and minuteness in patterning, uniformity in a light-emitting surface and precision in the edge of a light-emitting surface. The organic electroluminescent element is also required to solve such problems by a minute short-circuit occurring at an edge of an electrode, thereby causing cross talk in a display. There is known an element in which a sealing plate is clad to a substrate for the purpose of sealing an organic EL element. The sealing plate has the tendency to be thinner as a display is required to be thinner that is, minimized in the thickness.
However, a thin sealing plate results in a the problem that the sealing plate is brought into contact with an element by impact or external pressure with the result that the plate is destroyed.
Japanese Patent Application Laid-Open No.250583/1991 (Hei-3) discloses an organic EL element which is equipped with an interlaminar insulating film, and thus has favorable pattern precision as well as high uniformity in a light-emitting surface. However, since a masking vapor deposition method is applied to the production of a counter electrode, it has been still difficult to produce a highly precise and minute display having a line pitch of 300 xcexcm or less.
In addition, Japanese Patent Application Laid-Open No.101884/1993 (Hei-5) discloses an organic EL element which is equipped with an inter-insulator layer, and the outside surface of which is covered with a moisture-resistant film. Nevertheless the organic EL element thus disclosed has still a problem that because of the insufficient sealing power of the moisture-resistant film, a cathode is attacked by moisture or oxygen after being allowed to stand for several thousands hours, thus bringing about a dark spot, that is, defective light emission.
Moreover, Japanese Patent Application Laid-Open No. 275172/1993 (Hei-5) discloses a highly precise and minute display having a line pitch of about 100 xcexcm, by equipping an organic EL element with an inter-insulator layer in the form a wall, and also forming a cathode by means of oblique vapor deposition. However, the display disclosed above has still the problem a minute short circuit is caused by reason of the deviation of the alloy composition in the edges (the end away from the inter-insulator layer) of the electrode that is formed through vapor deposition in an oblique direction to the substrate.
An object of the present invention is to overcome the above-mentioned disadvantages inherent to the conventional techniques, and at the same time, to provide an organic electroluminescent element which is highly precise and minute, capable of uniformly emitting light, free from cross talk, capable of withstanding external pressure, and also excellent in sealing properties. It has been found that an organic electroluminescent element which is equipped with a vertically rising inter-insulator layer and With a sealing plate above the aforesaid film, is a highly precise and minute display which is free from cross talk, low in production cost, and can be miniaturized and made thinner.
The first aspect of the present invention provides an organic electroluminescent element 1 that is equipped, between a lower electrode 3 and a counter eletrode 4 each on a substrate 2, with an intervening organic layer 5 comprising a light-emitting layer, which element 1 comprises an inter-insulator layer 6 having a coefficient of water absorption of at most 0.1% in a non-light-emitting element portion; step portions 9 in said inter-insulator layer 6 which define the boundary between a light-emitting element portion and a non-light-emitting element portion and which contain rising parts almost perpendicular to the surface of said lower electrode 3; and a sealing plate or a sealing lid 7 which is placed over said inter-insulator layer 6 and which is attached to said substrate 2 via an adhesive layer 8. (Refer to FIG. 1.) The second aspect of the present invention provides a process for producing an organic electroluminescent element 1, comprising at least one step of forming a lower electrode 3 on a substrate 2; a step of forming a patterned inter-insulator layer 6 on said lower electrode 3; a step of forming an organic layer 5 on said lower electrode 3; and at least one step of forming a counter electrode 4 in the form of film, so that step portions 9 in said inter-insulator layer 6 define the boundary between a light-emitting element portion and a non-light-emitting element portion and also contain rising parts almost perpendicular to the surface of said lower electrode 3, said counter electrode 4 is cut off by said step portions 9 at the rising parts so as to be subjected to patterning processing, and said counter electrode 4 is in close contact with said inter-insulator layer 6 at said step portions 9 adjacent to said substrate 2.
The third aspect of the present invention provides an organic electroluminescent element 1 that is equipped, between a lower electrode 3 and a counter eletrode 4 each on a substrate 2, with an intervening organic layer 5 comprising a light-emitting layer, which element 1 comprises an inter-insulator layer 6 having a coefficient of water absorption of at most 0.1% in a non-light-emitting element portion; step portions 9 in said inter-insulator layer 6 which contain portions rising in the form of an inverse taper almost perpendicularly to the surface of the lower electrode 3 and divide said counter electrode 4 into a plurality of individuals; and a sealing plate or a sealing lid 7 which is placed over said inter-insulator layer 6 and which is attached to said substrate 2 via an adhesive layer 8.
The fourth aspect of the present invention provides an organic electroluminescent element 1 that is equipped, between a lower electrode 3 and a counter eletrode 4 each on a substrate 2, with an intervening organic layer 5 comprising a light-emitting layer, which element 1 comprises a first inter-insulator layer having a trapezoidal cross section 15 on said lower electrode 3 as a non-light-emitting element portion; a second inter-insulator layer 14 above said trapezoidal cross section(on the opposite side of said lower electrode 3); step portions 9 in said second inter-insulator layer 14 which contain rising parts almost perpendicular to the surface of the lower electrode 3 and divide said counter electrode 4 into a plurality of individuals; and a sealing plate or a sealing lid 7 which is placed over said second inter-insulator layer 14 and which is attached to said substrate 2 via an adhesive layer 8. (Refer to FIG. 2.)
The fifth aspect of the present invention provides a process for producing an organic electroluminescent element 1, comprising at least one step of forming a lower electrode 3 on a substrate 2; a step of forming a patterned inter-insulator layer on said lower electrode 3; a step of forming an organic layer over said lower electrode 3; and at least one step of forming a counter electrode 4 in the form of film so that a first inter-insulator layer 15 has a trapezoidal cross section, a second inter-insulator layer 14 is mounted above said trapezoidal cross section(on the opposite side of said lower electrode 3) step portions 9 in said second inter-insulator layer 14 contain rising parts almost perpendicular to the surface of said lower electrode 3, and said counter electrode 4 is subjected to patterning processing at said rising portions.